The present invention relates to an arrangement for measuring and/or monitoring an axial force applied to a shaft-like member such as a tool spindle of a machine tool.
The invention particularly relates to an arrangement for measuring and/or monitoring a force produced during feeding of a tool in material-removing operations, when the feeding is performed in the direction of an axis of a tool spindle, such as in drilling, abrading with conical tools and countersinking. Further fields of use of the present invention are those wherein variations of the axial force can serve as a characteristic of an operation.
Measurement and/or monitoring of an axial force applied to a tool spindle of a machine tool is very important in many cases. During material-removing operations the axial force is related to an axial component of a force on a cutting edge. An increase of the axial force serves for instance as an indication of an increased wear particularly on a main cutting edge. For this reason the axial force is considered as a certain characteristic of an operation so that information about the axial force can be used during the operation in self-adaptive control, that is, in a system for automatic optimization of operation-control action.
Arrangements for measuring an axial force have been proposed in the art. One known measuring arrangement includes a ring-shaped measuring element which is received in a spindle housing and located between an outer ring of a bearing of a spindle head and an associated axial stop face. This arrangement is not suitable for the above objects inasmuch as a direct contact of the outer ring of the bearing with a bore of the spindle housing produces a frictional force which considerably affects the output measurement by introduction of hysteresis effects.